Methods and systems for desiccant air conditioning

ABSTRACT

A desiccant air conditioning system for cooling an air stream entering a building space includes a conditioner and a regenerator. The conditioner includes structures arranged in a substantially vertical orientation that are spaced apart from each other with an air stream gap between each pair of adjacent structures. Each structure has a surface facing an air stream gap across which a liquid desiccant can flow. The air stream flows through the air stream gaps between the structures such that the liquid desiccant dehumidifies the air stream. Each structure further includes a separate desiccant collector at a lower end of the surface for collecting liquid desiccant that has flowed across the surface of the structure. The desiccant collectors are spaced apart from each other to permit airflow therebetween. A photovoltaic-thermal module heats a heat transfer fluid used to heat the liquid desiccant in the regenerator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 61/348,076, filed on May 25, 2010, entitled SOLARAIR-CONDITIONING AND HEATING SYSTEMS, and U.S. Provisional PatentApplication Ser. No. 61/430,692, filed on Jan. 7, 2011, entitled METHODSAND SYSTEMS FOR DESICCANT AIR CONDITIONING, both of which are herebyincorporated by reference.

BACKGROUND

The present application relates generally to air conditioning, capturingcombustion contaminants, desalination, and other processes using liquiddesiccants.

The term “air conditioning” generally refers to the treatment of airgoing into a building space, including to the heating, cooling, humidityadjustment, or purification of air that enters or leaves the space. Itis well known that air conditioning is an enormous source of energy useand that summer cooling in particular can lead to electricity gridproblems. Air conditioning is often the largest operating cost in abuilding.

Current air conditioning systems for cooling are generally based on thecompression of a gas such as Freon and the expansion of the compressedgas through a valve assembly. However, in order to reach the requiredhumidity levels of the entering air into a building, the air generallyneeds to be overcooled in order to condense water vapor into liquidwater. This dehumidification (latent cooling) generally uses more energyin an air conditioning system than the physical lowering of the airtemperature (sensible cooling). Oftentimes re-heaters are employedwithin an air conditioner requiring even larger amounts of energy.

Air conditioning for heating air is typically done by combustion ofnatural gas or some other fuel. The combustion often heats a heattransfer fluid that is then directed to a fan coil unit where theentering air is heated. In many buildings, such sensible only heatingresults in humidity levels that are too low for comfort. Oftentimeshumidifiers are integrated with the heating system. Such humidificationhowever results in the cooling of the air, which means that additionalheating will have to be applied to counteract the cooling effect of thehumidifier.

Solid desiccant systems have been used for many years primarily forsummer cooling. However, the heating effect that occurs when air isdehumidified in an adiabatic fashion (no heat is added or removed)requires large amounts of sensible cooling post-dehumidification and asa result limits the energy savings that can be obtained.

Absorption chillers such as units manufactured by Yazaki Energy Systemstypically utilize a low pressure vacuum vessel in which a desiccantmaterial is contained (in Yazaki's case LiBr2 and water, but systemsusing Silica gel have also been developed). However, the use of lowpressure vacuum systems significantly increases the cost and complexityof the equipment and increases the requirements for maintenance. Also,each transition (from air to a heat transfer fluid to the desiccant)utilizes heat exchangers, fans, and pumps and thus results in highercosts. And importantly, such transitions result in larger temperaturerequirements since each transition is not perfectly efficient. As aresult, absorption chillers require higher temperatures to operatemaking them less suitable for integration with systems that employ wasteheat or low grade heat.

More recently systems have been introduced that employ other methods fordehumidification of the air. Liquid desiccant systems such as thesystems manufactured by DuCool and Agam use a strong desiccant materialsuch as a CaCl₂ and water or LiCl₂ and water solution to absorb watervapor in the air. The liquid desiccant is directly exposed to the airunlike the previously discussed absorption chillers that do not have airto desiccant direct contact. After the desiccant absorbs moisture fromthe air stream, it is heated to release the excess water. In winter,such desiccants can be used to recover heat and moisture from theleaving air and transfer it to the incoming air.

Liquid desiccant systems however have traditionally suffered from therisk of desiccant carry-over into the air stream resulting in sometimessevere corrosion problems in the building since the desiccants that areused are typically strongly corrosive to metals.

Furthermore, liquid desiccant systems are typically spraying a liquiddesiccant on a filter media to increase the surface area of desiccantexposed to the air. The spraying increases the risk of desiccantcarryover into the air stream. Oftentimes additional mist eliminatorfilters are used to capture any airborne desiccant particles. However,these mist eliminators require frequent maintenance and replacement.Furthermore, the process of using a filter media is inherently energyinefficient. The filter media is an obstruction in the air flow and thusgenerally requires large fan power. Also, the filter media typically arethermally non-conductive which makes the dehumidification processadiabatic resulting in undesirable heating of the air. To counteract theheating effect, one can increase the flow rate of the desiccant and onecan pre-cool the desiccant to achieve some level of sensible cooling atthe dehumidification stage in the filter media. Increasing the flow rateof course increases the risk of desiccant carry over and requires moreliquid pump power. The liquid desiccant typically “rains” down from thefilter media into a liquid desiccant collection pan. This generallyprevents the liquid desiccant system from using a vertical air flow andrequires more costly duct work to be used during the installation of thesystem on a buildings roof, where air is typically handled vertically.Furthermore, the drain pans do not easily allow the system to be set upas a “split” system wherein the conditioner and regenerator are locatedin physically separate locations. In addition, the drain pans do noteasily allow for the system to be expandable: one has to increase thesize of the pan—which means a new design, rather than adding capacitythrough a scalable design.

AIL Research has developed a low flow desiccant system that overcomessome of the objections mentioned above. The use of a heat transfer fluidin-situ to where the desiccant is dehumidifying the air results inbetter thermal performance and lower fan and pump power. However thisapproach still utilizes a horizontal air flow—which makes it much harderto integrate to a rooftop installation—and a very complex conditionerdesign that has a desiccant drain pan at the bottom, but does not allowfor a counter flow between the air and the liquids. This system alsostill has the risk of desiccant carryover since the desiccant is stilldirectly exposed to the air flow.

The source of heat and the required temperature for regeneration of thedesiccant is also an important consideration in the design of a solarair conditioning system. It should be clear that the lower theregeneration temperature of the desiccant is, the easier it should be tofind a source of such (waste) heat. Higher regeneration temperaturesnecessitate higher quality (temperature) heat sources and thus are lesseasily available. At worst, the system has to be powered by a non-wasteheat source such as a hot water furnace. Yazaki absorption units havebeen powered by evacuated tube solar thermal modules that are able togenerate heat as high as 100° C. Concentrated solar thermal modules areable to achieve even higher temperatures, but oftentimes do so at highercosts. Glazed flat plate solar thermal collectors typically operate atsomewhat lower temperatures of 70-80° C., but also lose a significantportion of their efficiency at higher temperature, which means that thearray size needs to be increased to generate adequate power. Unglazedflat plate solar thermal collectors have higher efficiencies at lowertemperatures, but generally lose a lot of their efficiency at hightemperatures and are usually not able to achieve temperatures higherthan 60° C., making them unsuitable for integration with absorptionchillers.

None of the solar heat sources mentioned above (concentrated solarthermal, evacuated tube collectors and glazed and unglazed flat platecollectors) generates electricity at the same time as generating heat.However, all air conditioning systems still require electricity for fansand liquid pumps. Electricity is oftentimes much more expensive per unitof energy than fuels used for heat. It is therefore desirable to have anenergy source that can provide heat as well as electricity.

It is known that solar Photo-Voltaic Modules (PV modules) heat upsignificantly in direct sun exposure with temperatures approaching70-80° C. Such temperatures have a deteriorating effect on theperformance of the module since module performance degrades with anincrease in temperature. Applying a thermal transfer fluid to the backof the PV module (a module known as a PVT (PV-Thermal) module)effectively draws the heat from the module, lowering its temperature andincreasing its efficiency. The thermal transfer fluid (typically wateror water and propylene or ethylene glycol) can reach temperatures andthermal efficiencies typically between those of a glazed and an unglazedsolar thermal module.

From a cost perspective, solar thermal systems augmented withconventional PV modules are less cost effective than PVT modules andtake up more space than PVT modules. However, PVT modules generallysupply lower temperatures and efficiencies than pure solar thermalsystems. But beneficially they generate more electricity thanconventional PV modules.

BRIEF SUMMARY

As discussed in further detail below, various embodiments disclosedherein are directed to methods and systems for air conditioning,capturing combustion contaminants, desalination, and other processesusing liquid desiccants.

In accordance with one or more embodiments, solar Photo Voltaic-Thermal(PVT) modules are connected to a desiccant air conditioning system toheat desiccants. The PVT modules can be connected in variousarrangements for summer cooling and winter heating. The air conditioningsystems can include both horizontal and vertical air flow desiccantsystems, including spray-head desiccant systems.

In accordance with one or more embodiments, the PVT modules can be usedto provide cold water for a desiccant system for summer cooling.

In accordance with one or more embodiments, the PVT modules can be usedto provide heat for water going to a humidifier of air in a desiccantair conditioning system.

In accordance with one or more embodiments, the air conditioning systemscan include a set of hollow plate structures used to expose desiccant toan air flow. In accordance with one or more embodiments, the platestructures have a wavy shape aspect to them. The hollow wavy platestructures are constructed in such a way that the surface tension of theliquid desiccant is used to draw the liquid desiccant into a drainchannel. In accordance with one or more further embodiments, a sheetmaterial such as a membrane or wetting material can be arranged on thewavy plates to guide a liquid desiccant into the drain channel. Amembrane can be a micro-porous membrane with pores ranging in size fromtypically from 0.01 μm to 1 μm. An example of such a membrane is amembrane made by Celgard of Charlotte, N.C., and a division of PolyporeCorporation, under the type designation EZ2090.

In accordance with one or more embodiments a membrane is a micro-porousmembrane backed by a material intended to evenly distribute a liquid. Inembodiments a membrane is a hydrophobic microporous membrane. Inembodiments the backing material is a hydrophilic material such as awicking material. An example of such a wicking material is theinterfacing material made by the Pellon Company of New York, N.Y.

In accordance with one or more embodiments, the wavy plate structuresare arranged in the air conditioning system such that the liquiddesiccant is exposed to a vertical air flow without substantiallyobstructing the air flow.

In accordance with one or more embodiments, multiple sets of wavy platestructures can be arranged into a stack that has a scalable naturewherein the drying or wetting capacity of the desiccant can easily beexpanded by simply adding additional wavy plates.

In accordance with one or more embodiments, a membrane desiccant systemis provided for an air conditioning system using counter-flows ofliquids and air in a vertical air flow system.

In accordance with one or more embodiments, a membrane desiccant systemis provided wherein a membrane or other hydrophobic material is bondedto a wetting or other hydrophilic material in such a way as the provideproper distribution of a liquid behind the membrane. In embodiments to adouble layer is bonded to a (thermally conductive) hydrophobic structuresuch as a plastic cooling channel or support plate.

In accordance with one or more embodiments, the plate constructionallows for spreading a liquid desiccant at the top of a plate and forcollecting such desiccant at the bottom of the plate.

In accordance with one or more embodiments, the air flow going to avertical air flow desiccant set of wavy plates is preheated, and the airleaving a set of plate structures is post-cooled.

In accordance with one or more embodiments, plate structures areconstructed and assembled in such a way that the plates can thermallyconduct heat, but are still corrosion resistant by employing a thermallyconductive plastic material. In embodiments such a plastic has a thermalconductance of about 5 to 10 W/mK. As an example thermal conductancesfor regular plastics range from 0.1 to 0.5 W/mK, whereas Copper,Aluminum, Stainless Steel and Titanium have a conductance of about 400,250, 16 and 18 W/mK respectively. Of these materials only Titanium isreasonably suitable for use with desiccants such as CaCl₂ or LiCl₂ dueto the corrosive nature of the desiccants.

In accordance with one or more embodiments, plate structures areassembled using a header that can be stacked vertically as well ashorizontally in such a way that the wavy plates can be stacked parallelto each other as well as on top of each other.

In accordance with one or more embodiments, plate structures areassembled in such a way that a membrane is mounted on each plate toguide liquid desiccant to a header at the bottom of the wavy plate.

In accordance with one or more embodiments, the air inlet to the platestructures is disturbed by a mesh or set of disturbance plates in such away as to create turbulent air movement in the air entering the wavyplates.

In accordance with one or more embodiments, a solar inverter isintegrated an air conditioning system in such a way that the electricalconnections to the air conditioning system provide the electricalconnection to the building for a set of solar modules. In someembodiments, the air conditioning unit is a desiccant air conditioningsystem. In some embodiments, the desiccant air conditioning system usesvertical air flows. In some embodiments, the solar modules are PVTmodules.

In accordance with one or more embodiments, a liquid desiccant verticalair flow system utilizes a chiller as a source of cold water and a gaswater heater as a source for warm water, wherein the gas water heater issupplemented by the heat generated by solar modules.

In accordance with one or more embodiments, a PVT module provideselectrical power and heat to a desiccant air conditioning system andprovides heat to a water storage tank. The hot water can gradually bestored in tanks underneath the PVT modules, and the electrical power canbe used to operate the air conditioning system. Any excess electricalpower can be provided to other devices.

In accordance with one or more embodiments, PVT modules are set up insuch a way as to radiate heat during the night, and thus provide coolingof water. Such cooled water can be stored in water storage tanks so thatit can be made available during the day for the cold side of a desiccantair conditioning system. In some embodiments, such cold water can alsobe generated at night using an evaporative chiller in combination withthe PVT modules.

In accordance with one or more embodiments, a PVT module generates hotwater that is regulated by a thermostatic switch so as to enter a tankor flow directly to a manifold. In some embodiments, the thermostaticswitch is driven by the temperature of the hot water. In someembodiments, the switch is operated by remote control.

In accordance with one or more embodiments, water is stored in a tankunderneath a PVT module in such a way that the tank provides adequateevenly distributed weight to function as a ballast and support systemfor the PVT module. In some embodiments, the tank has a removable lid.In some embodiments, the tank can furthermore function as a shippingcontainer for the module.

In one or more embodiments, PVT modules are connected to a platestructure desiccant system. In some embodiments, the wavy plate systemis set up to provide cool air to a building. In some embodiments, thewavy plate system is set up to provide warm moist air to a buildingspace.

In accordance with one or more embodiments, PVT modules are connected sothat they preheat water that is destined to go into a humidifier for airdestined for a building space.

In accordance with one or more embodiments, a desiccant is separatedinto various layers in a vessel wherein the concentration of thedesiccant varies along the height of a vessel. In some embodiments, thevessel is used to provide and collect desiccant to a desiccant airconditioning system. In some embodiments, at least one of the outlets ofthe vessel is adjustable so that different layers with differentdesiccant concentrations can be selectively drawn from the vessel.

In accordance with one or more embodiments, a portion of an air flowtreated by a plate conditioner in such a way that the humidity isreduced is diverted to an additional set of plates that provides coolingof the air through evaporation of water vapor. In some embodiments, sucha system uses membranes on the surface of the plates. In someembodiments, the air flow across the second set of plates can bereversed and the water for evaporation replaced by a desiccant in such away that during winter operation, it provides additional heatingcapacity of the air entering the building.

In accordance with one or more embodiments, a set of plate structuresprovides an evaporative cooling effect and the so produced chilledliquid is directed to both a conditioner as well as one or more liquidto air heat exchangers. In embodiments such liquid to air heatexchangers are ceiling panels. In embodiments such liquid to air heatexchangers are fan coils. In embodiments such fan coils are locatedinside ductwork. In embodiments such liquid to air heat exchangers arelocated underneath a floor.

In accordance with one or more embodiments, a series of holes isprovided at the top of the membrane to inhibit vacuum lock and allow foreasy draining of desiccant from behind the membrane covering a platestructure.

In accordance with one or more embodiments, a plate structure isconstructed in such a way as to provide alternating access to water andliquid desiccant on the surface of the plates by providing holes on anasymmetrical pattern.

In accordance with one or more embodiments, a heat exchanger isconstructed using thermally conductive plastic plates to provide heattransfer between corrosive fluids. In some embodiments, such a plateheat exchanger uses horizontal and vertical counter flows. In someembodiments, the thermally conductive plates are formed in such a way asto have ridges and features that promote heat exchange and areconstructed so that they can be stacked and sealed. In some embodiments,the thermally conductive plastic plates are not formed, but rather agluing material is used to create and attach ridges on the top and/or onthe bottom of the plastic plates. In some embodiments, the gluingmaterial is also used to provide a seal to the liquids in between theplates. In embodiments the glue ridges are shaped in such a way that theridges on the lower plate are supporting the ridges on the top of theupper plate, while the seal glue spans the entire gap between the twoplates. In embodiments, the glue material is Marine 5200, made by 3MCorporation of St. Paul, Minn.

In accordance with one or more embodiments, a first set of platestructures is contained in a hermetically sealed container and wherein asecond set of plates is contained on the opposite side of the container.The first set of plates contains an optional membrane over its surfaceor a wetting material. The first set of plates receives a diluteddesiccant from a desiccant source. The first set of plates also receivesa heated heat transfer fluid from a source. A fan provides air movementinside the hermitically sealed container in such a way that water vaporis taken from the first set of plates. The second set of plates isrelatively cool compared to the air environment and the enclosure insuch a way as to cause condensation of water on its surfaces. The watercan be withdrawn from the sealed enclosure. In some embodiments, thesecond set of plates is cooled by an external cold source.

In accordance with one or more embodiments, a set of plate structureswith a liquid desiccant exposed to its surface collects moisture from anair stream and directs the diluted desiccant to a hermitically sealedcontainer wherein the desiccant is regenerated and wherein the watervapor is recovered in the form of liquid water. In some embodiments, theheat for the system is provided by solar thermal modules. In someembodiments, the heat for the system is provided by PVT modules.

In accordance with one or more embodiments, a liquid desiccant is firstregenerated in a hermitically sealed container and subsequentlyregenerated in an open array of plate structures. In some embodiments,the water recovered in the hermitically sealed container is diverted toa set of plate structures providing an evaporative cooling effect.

In accordance with one or more embodiments, fuel combustion takes placein such a way that the effluent gasses are directed through a set ofplate structures having a liquid desiccant on its surfaces. The effluentgasses contain substances such as Carbon Dioxide, Water Vapor andcontaminants such as SO_(x) and NO_(x), which can be captured into thedesiccant. In some embodiments, the desiccant is regenerated into aconcentrated desiccant and liquid water. In some embodiments, thedesiccant is filtered in such a way as to remove acidity created by theSO_(x) and NO_(x) and other gasses absorbed from the fuel combustionprocess.

In accordance with one or more embodiments, a desiccant draws waterthrough a membrane from a water source such as seawater. Theconcentrated desiccant is diluted as a result of the transition of waterthrough such membrane. The diluted desiccant is transported to ahermetically sealed enclosure wherein the desiccant is regenerated insuch a way that concentrated desiccant and liquid water are produced. Insome embodiments, the heat for regeneration is provided by solar thermalmodules. In some embodiments, the heat for regeneration is provided byPVT modules.

Many construction variations can be envisioned to combine the variouselements mentioned above each with its own advantages and disadvantages.The present invention in no way is limited to a particular set orcombination of such elements.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates a desiccant air handling system using a shower headdesign in accordance with the prior art.

FIG. 1B illustrates a desiccant air handling system using a plate designand horizontal air flow in accordance with the prior art.

FIG. 2A shows a desiccant air handling system set up for extreme summeroperation with cold source and PV/Thermal module tie-in in accordancewith one or more embodiments.

FIG. 2B shows a desiccant air handling system set up for non-extremesummer operation with cold source and PV/Thermal module tie-in inaccordance with one or more embodiments.

FIG. 3A shows a desiccant air handling system set up for extreme winteroperation with cold source and PV/Thermal module tie-in in accordancewith one or more embodiments.

FIG. 3B shows a desiccant air handling system set up for non-extremewinter operation with cold source and PV/Thermal module tie-in inaccordance with one or more embodiments.

FIG. 4 shows the integration between a building's existing airconditioning system, a desiccant air conditioning system and PVT modulesin accordance with one or more embodiments.

FIG. 5 shows a desiccant system employing a vertical air flow inaccordance with one or more embodiments.

FIG. 6A depicts a three-dimensional view of the system of FIG. 5 inaccordance with one or more embodiments.

FIG. 6B depicts one or more turbulence plates that create air turbulencein the air entering a set of plate structures.

FIG. 7 shows the vertical air flow desiccant system with optional pre-and post air treatment coils and heat pump system in accordance with oneor more embodiments.

FIG. 8 depicts details around the wavy plate structures in accordancewith one or more embodiments.

FIG. 9 shows a possible construction for the wavy plate structures inaccordance with one or more embodiments.

FIG. 10A shows an alternative method for wavy plate structure assembly,including the mounting of a membrane or wicking material in accordancewith one or more embodiments.

FIG. 10B shows a cross section of two membranes with a hydrophilicwicking material sandwiched in between two hydrophobic membranes whereinthe wicking material spreads a liquid uniformly between the twomembranes in accordance with one or more embodiments.

FIG. 10C shows a cross section of a hydrophobic membrane, a hydrophilicwicking material and a (thermally conductive) support wall in accordancewith one or more embodiments.

FIG. 10D shows a cross section of two membranes with two wickingmaterials and an internal (thermally conductive) support wall inaccordance with one or more embodiments.

FIG. 10E shows a cross section of two membranes with two wickingmaterials and an internally hollow (thermally conductive) support wallin accordance with one or more embodiments.

FIG. 11A shows how the plate structures can be stacked into largerarrays and depicts construction details in accordance with one or moreembodiments.

FIG. 11B illustrates desiccant system employing a horizontal air flowthrough two conditioners in accordance with one or more embodiments,wherein the air is treated twice by plates that are oriented at an angleto the air flow.

FIG. 11C shows a top view of the embodiment of FIG. 11B.

FIG. 11D shows the arrangement from FIG. 11B replicated twice in such away as to treat the incoming air into a space and to recover energy fromthe returning air in a second set of conditioners in accordance with oneor more embodiments.

FIG. 11E shows a desiccant membrane plate stack in the prior art thatuses a portion of the dehumidified air for indirect evaporative coolingin accordance with one or more embodiments.

FIG. 11F illustrates a section of a desiccant membrane plate stack thatuses a portion of the dehumidified air to provide indirect evaporativecooling in a controllable fashion

FIG. 11G shows a close up cut away detail for the bottom of the platestack in FIG. 11F.

FIG. 11H illustrates further details of some of the components shown inFIG. 11F.

FIGS. 11I and 11J show a three dimensional and top view, respectively,of an embodiment that uses a tube structure for exposing liquiddesiccant to air streams while providing a simultaneous heating orcooling functions in accordance with one or more embodiments.

FIGS. 11K and 11L illustrate a three dimensional and top view,respectively, of a hexagonal structure for exposing liquid desiccant toan air stream while providing heating or cooling functions in accordancewith one or more embodiments.

FIG. 12 depicts a complete solar air conditioning system including asolar PV/Thermal array in accordance with one or more embodiments.

FIG. 13A demonstrates how storage and PVT modules can be used to createa hot/cold offset cycle for a desiccant air conditioning system duringthe day in accordance with one or more embodiments.

FIG. 13B demonstrates how storage and PVT modules can be used to createa hot/cold offset cycle for a desiccant air conditioning system duringthe night in accordance with one or more embodiments.

FIGS. 14A and 14B show a PV/Thermal module with integrated hot waterstorage/ballasting system in accordance with one or more embodiments.

FIGS. 15A and 15B show how the ballast tank and storage system candouble as a shipping container for the PVT module in accordance with oneor more embodiments.

FIGS. 16A and 16B demonstrate how PVT modules and cold sources can beintegrated into the wavy plate desiccant system for summer operation inaccordance with one or more embodiments.

FIGS. 17A and 17B demonstrate how PVT modules can be integrated into thewavy plate desiccant system and humidifiers for winter operation inaccordance with one or more embodiments.

FIGS. 18A and 18B show how the heat from storage or PVT modules can beused during the day and during the night for air conditioning operationin accordance with one or more embodiments.

FIG. 19A shows how a desiccant concentration separator and evaporativecooler can be integrated into the wavy plate system during summeroperation in accordance with one or more embodiments.

FIG. 19B shows the system of FIG. 19A integrated to a building spacewherein the chilled water that is produced by the evaporative cooler isnot only used for cooling the conditioner but also used for coolingceiling panels or floor panels.

FIG. 20A shows how the additional wavy plates in FIG. 19A can be used toincrease heating capacity during winter operation in accordance with oneor more embodiments.

FIG. 20B shows how a portion of the air entering a conditioner can bedrawn out of the conditioner and diverted to a third set of wavy platesfor winter operation.

FIG. 21A shows a corrosion resistant heat exchanger with thermallyconductive plastic plates in accordance with one or more embodiments.

FIG. 21B shows a different embodiment of a corrosion resistant heatexchanger with thermally conductive plastic plates in accordance withone or more embodiments.

FIG. 21C shows the major manufacturing steps involved in using gluestructures to construct a fluid to fluid heat exchanger in accordancewith one or more embodiments.

FIG. 22 shows a water recovery system using plate structures inaccordance with one or more embodiments.

FIG. 23 shows a desiccant system for heating and dehumidification inaccordance with one or more embodiments.

FIG. 24A shows a heating and dehumidification system using the wavyplates and a water recovery system in accordance with one or moreembodiments.

FIG. 24B shows a dual effect desiccant regeneration system which usesrecovered liquid water for indirect evaporative cooling.

FIG. 25 shows a desiccant air conditioning system which captures andcondenses combustion gasses and recovers water in accordance with one ormore embodiments.

FIG. 26 shows a desiccant air conditioning system setup for winterheating that also condenses water vapor and captures contaminants fromthe combustion process in accordance with one or more embodiments.

FIGS. 27A and 27B show a three-dimensional model of the system of FIG.24A in accordance with one or more embodiments.

FIG. 28 shows the water recovery system of FIG. 22 integrated to adesalination system for water purification in accordance with one ormore embodiments.

Like reference characters generally denote like parts in the drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1A depicts a liquid desiccant air conditioning system as known inthe prior art. A desiccant conditioner 102 contains a liquid desiccantin a bath 104. The liquid desiccant 104 can be any suitable solutionthat attracts water vapor from the outdoor air 110 that is blown intothe conditioner 102. The air moves through a filter media 106 thatusually comprises a convoluted surface that easily holds and exposes thedesiccant to the air stream. Examples of desiccants include CaCl₂ andLiCl₂. The filter media can be a cellulosic cooling tower fill material.Diluted desiccant 105 that has absorbed water drips from the filtermedia 106 into the desiccant bath 104. The spray head 107 distributesthe concentrated desiccant evenly across the filter media 106.Dehumidified and cooled air 111 is directed into the building. A portion(usually around 10%) of the diluted desiccant 112 is brought through aheat exchanger 103 to a regenerator 101. The majority of the desiccant112 is brought back to the spray head 107 at the top of the conditioner102 through an optional cold source 113. The desiccant that is divertedto the regenerator 101 is heated in an optional heater 114 and pumped toa spray head 107′ similar to the spray head on the conditioner side. Theheated desiccant falls onto a filter media 106′ and drips down 105′ intoa desiccant bath 104′. Return air from the building or outdoor air 108is brought through the filter media and absorbs water from the desiccantsuch that moist hot air 109 is exhausted from the regenerator. Asdiscussed earlier, the drawbacks of this system are that the absorptionof water vapor into the desiccant is an almost adiabatic processresulting in heating of the air that is meant to be cooled. Furthermorethe spray head can lead to some desiccant being carried over into theleaving air streams 111 and 109. And lastly, the baths 104 and 104′force the air flows 110 and 108 to be horizontal and vertical throughthe filter media. This makes installation on a building roof morecomplicated since the exiting air 111 needs to be ducted into a downwarddirection and the return air 108 from the building needs to be ductedinto a horizontal aspect.

FIG. 1B is an alternate system known in the prior art. The conditioner121 comprises a set of vertical plates 118 (which are constructed to behollow inside) and a desiccant collector 120. Chilled heat transferfluid from a cold source 113 is brought inside the plates 118 and formsa U-shaped loop 116 internal to the plate. A concentrated desiccant 119is run over the surface of the plates 118. Outdoor air 110 is directedover the desiccant 119 in a horizontal orientation. The desiccantabsorbs water vapor from the air and runs down the surface of the plates118 into the desiccant collector 120. The diluted desiccant 121 ispumped through a heat exchanger 103 to the regenerator 122. Theregenerator comprises a set of plates 117 that again are hollow and thathave U-shaped channels 116′ in them. Diluted desiccant 119′ is again runover the surface of the plates 117 that are heated by the hot transferfluid source 114. Outdoor air or return air from the building 108 isused to absorb water vapor from the desiccant 119′. The desiccant getsmore concentrated as it runs down the surface of the regenerator andcollects into the desiccant collector 115. As in the previous example,the air flow in the desiccant system is primarily horizontal resultingin the need for additional ducts to be used for installation on arooftop. A horizontal air flow would have been preferred because no ductwork would have been necessary, but the desiccant collectors 115 and 120generally block air from flowing vertically. Furthermore, the U-shapedchannels do not allow for a counter-flow design between the air,desiccant, and cooling or heating fluids resulting in lower thermalefficiency of both the conditioner and the regenerator. As compared tothe system in FIG. 1A, the liquid desiccant system in FIG. 1B uses lowerfan power and lower desiccant pump power.

FIG. 2A shows a liquid desiccant system in accordance with one or moreembodiments configured for extreme summer operation and so as tointegrate with and optional heat pump 201. A portion of the desiccant inthe conditioner 102 is brought through a heat exchanger 202 that can becoupled to a PVT module array. Since the typical desiccant materialsthat are used are corrosive to metals, the use of a heat exchanger isdesirable. This also complicates the integration of the heat pump 201;since the desiccant should not contact any metal parts, the heattransfer is made indirectly through a specially designed heat exchanger.As can be seen in the figure, desiccant is taken from the conditioner,is heated in the PVT modules 202 or by the heat pump 201 and sprayedinto the regenerator 101. Conversely concentrated desiccant is takenfrom the regenerator 101, run through an optional cold source 203 orthrough the cold side of the heat pump 201 and into the conditioner.

In FIG. 2B a similar set up is shown for non-extreme operation. The maindifference is that the desiccant from the conditioner is cooled, and putback into the conditioner side rather than also being transported to theregenerator. Desiccant only transfers to the regenerator through theheat exchanger 103. Similarly the desiccant in the regenerator is onlyheated and put back into the regenerator itself rather than being putinto the conditioner.

In extreme winter operation in FIG. 3A, the heat sources 201 and 202 arenow heating the liquid desiccant as it is transported to the conditioner102. It is noted that the conditioner in the winter setup is used to addwater vapor and heat to in incoming air stream 110 and conditions theair to have a higher temperature and humidity as it enters the buildingat 111. It is also possible to add a humidifier 301 that can bepreheated by another PVT module array 302 or by another source ofthermal energy. Since the water that is brought into the humidifier 301is not corrosive to metals, it is not per-se necessary to use a heatexchanger in 302; the water can be heated directly by the PVT modules.It is further worth noting that the return air 108 from the buildinggenerally is higher in temperature and humidity than the outside air110. The regenerator 101 in this setup actually captures the heat andmoisture from the return air and transports it to the outdoor air,resulting in much lower heating costs and the desiccant system is inthis setup effectively functioning as an enthalpy recovery system.

In FIG. 3B a similar setup is shown as in FIG. 3A, except now the heatsources 201 and 202 are now used to heat the desiccant on theconditioner 102 side of the system directly. Similarly the cold side ofthe heat pump 201 can directly draw heat from the desiccant in theregenerator.

The cold source 203 in FIGS. 3A and 3B will in most cases not be neededduring winter operation of the system. It is also noted that thedesiccant in winter mode will need to be diluted which means that smallamounts of water will need to be added on a regular basis in order toprevent overconcentration of the desiccant. This water can come from thereturn air from the building, but may still need to be supplemented fromother sources.

FIG. 4 shows how the enthalpy recovery system from FIG. 3A can beintegrated into an existing building air conditioner infrastructure. Thebuilding space 401 is connected by ducts 402 to the desiccant systemfrom FIG. 3A. The existing air conditioner heat pump comprisingcompressor 403 releases heat through fan coil 405 and the incoming aircan be supplementally heated by PVT modules 406 and an additional fancoil. The compressed gas expands at the valve 407 and is heated by thereturn air in fan coil 404 before returning to the compressor 403. Theabove described setup significantly reduces the load on the airconditioning system by again recovering both heat and water vapor.

In FIG. 5 a new type of liquid desiccant system is shown. Theconditioner 501 comprises a set of plate structures that are internallyhollow. Optionally the plate structures can have a wavy shape applied tothem. The term wavy as used herein refers broadly to a variety ofconvoluted structures, including serpentine or undulating shapes. A coldheat transfer fluid is generated in cold source 507 and entered into theplates. Liquid desiccant solution at 514 is brought onto the outersurface of the plates and runs down the outer surface of each of theplates. In some embodiments, the liquid desiccant runs in a wickingsurface that significantly increases the area of desiccant exposed tothe air stream 503. In other embodiments—described further below—theliquid desiccant runs behind a thin membrane that is located between theair flow and the surface of the plates. Outside air 503 is now blownthrough the set of wavy plates. The liquid desiccant on the surface ofthe plates attracts the water vapor in the air flow and the coolingwater inside the plates helps to inhibit the air temperature fromrising. The plate structures are constructed in such a fashion as tocollect the desiccant near the bottom of each plate thereby eliminatingthe need for a desiccant collector or bath as was shown in FIGS. 1A and1B. The treated air 504 is now put in the building directly without theneed for any additional ducts. Furthermore, since all flows of air, heattransfer fluids and desiccant are vertical, the system is thermally moreefficient. The wavy shape of the plates has two primary advantages: airis more easily brought in contact with the surface of the plates sincethe wavy shape constitutes more of a convoluted path than a straightplate would have given. But importantly, the wavy shape allows for theplates to expand sideways without putting undo stresses on theconnections for heat transfer fluids and desiccants at the top andbottom of the plates. This is particularly important since the wavyplates should be constructed from a material that is compatible with thedesiccant being used, for example from a (thermally conductive) plasticmaterial such as a thermally doped polymer extrusion. Typically such aplastic has a thermal conductance of about 5 to 10 W/mK. As an examplethermal conductances for regular plastics range from 0.1 to 0.5 W/mK,whereas copper, aluminum, stainless steel and titanium have aconductance of about 400, 250, 16 and 18 W/mK respectively. Of thesematerials only Titanium is reasonably suitable for use with desiccantssuch as CaCl₂ or LiCl₂ due to the corrosive nature of the desiccants.The wavy plates in the regenerator 502 will expand under the highertemperatures for regenerating the desiccant. This can create thermalstresses on the assembly. The wavy shape helps to reduce those stressesby allowing the plates to expand sideways rather than in the verticaldirection.

The liquid desiccant is collected at the bottom of the wavy plates at511 and is transported through a heat exchanger 513 to the top of theregenerator to point 515 where the liquid desiccant is distributedacross the wavy plates of the regenerator. Return air or optionallyoutside air 505 is blown across the regenerator plate and water vapor istransported from the liquid desiccant into the leaving air stream 506.An optional heat source 508 provides the driving force for theregeneration. The hot transfer fluid 510 from the heat source can be putinside the wavy plates of the regenerator similar to the cold heattransfer fluid on the conditioner. Again, the liquid desiccant iscollected at the bottom of the wavy plates 502 without the need foreither a collection pan or bath so that also on the regenerator the aircan be vertical. It should be clear to those skilled in the art that thewavy plates can be easily expanded to add additional cooling or heatingcapacity, that these plates provide for better heat transfer and thatthe elimination of any bath or collection pan allows for the system tobe directly mounted on a roof opening without the need for additionalduct work. An optional heat pump 516 can be used to provide cooling andheating of the liquid desiccant similar to the method employed in FIG.1A. It will be clear to those skilled in the art that the absence of aliquid bath or collection pan also enables the easy installation of theconditioner 501 in a remote location from other components in thesystem, such as are commonly used in what is know as “split” airconditioning systems.

It will furthermore be clear to those skilled in the art that the systemof FIG. 5 can be made relative small in size in such a way that thesystem could be integrated into an automobile or other vehicle. In suchan automobile the heat source 508 can potentially be the heat from anengine and cooling could be provided by a Peltier cooling system.

In FIG. 6A the system of FIG. 5 is shown in a 3 dimensional projection.Desiccant fluid pumps 601 provide the transportation of the desiccantbetween the conditioner and the regenerator. The holes 602 at the top ofwavy plates 501 and 502 ensure an even distribution of desiccant overthe surface of the wavy plates. Groves 603 at the bottom of the wavyplates 501 and 502 collect the desiccant by using either the naturalsurface adhesion of the desiccant to the plastic of the wavy plates togather the desiccant into the grove or by using some membrane or otherwetting material to help collect the desiccant into the groove. The heattransfer fluid can be connected to the wavy plates at connections 604,605, 606 and 607.

FIG. 6B shows how the inlet air 652 of a set of wavy plates 502 can bemade turbulent by a set of plates 651. The plates 651 are constructed insuch a way as to impart turbulent airflow to the air entering the wavyplates 502. The resulting turbulent air will better exchange heat andmoisture with the surface of the wavy plates as compared to air thatflows through the wavy plates in laminar fashion.

FIG. 7 depicts the system similar to FIG. 5 with the addition of a postconditioner cooling coil 702 and preheating coil 701 for theregenerator. An alternate configuration for the heat pump 705 is toinstead of heating the desiccant as in FIG. 5, to heat the heat transferfluid with heat exchanger coils 703 and 704. The eliminates the need tohave the heat exchanger use corrosion resistant components allowing fora more standard heat exchanger to be used.

FIG. 8 shows a close-up view of one embodiment of the wavy plateassembly where the desiccant drain 801 at the bottom of the platescollects the desiccant that has run into the groove 811. Heat transferfluid is connected to the plates at 802 and 805. The main body of thewavy plates 803 can be made from a suitable material that exhibits goodthermal conductivity as well as corrosion resistance, for example athermally conductive plastic extrusion. Liquid desiccant is entered intothe distribution channel 806 at the top of the plates 807 and exits theholes 810 at the top of same plates and runs over the surface 804. Theheat transfer fluid 808 runs inside openings 809 in the wavy plates. Ascan be seen from the figure the construction of the grooves 811 allowsthe desiccant to collect at the bottom of each individual plate withoutobstructing the air flow and without the need for a separate commoncollection pan. It should be obvious to those skilled in the art thatthe entering air stream 812 and exiting air stream 813 can be reversedand also that the direction of the heat transfer fluid between 802 and805 can be either upwards or downwards. The desiccant itself wouldnormally run down the surface because of the force of gravity acting onthe desiccant.

FIG. 9 shows further details of one embodiment of the construction ofsuch wavy plates. A component 901, which is preferably an injectionmolded plastic component, is bonded on the thermally conductiveextrusion 902. It should be obvious to those skilled in the art thatother manufacturing methods can be employed such as machining,thermoforming, welding and other suitable methods. Other materials forthe components can be suitably selected to be compatible with thecorrosive nature of typical desiccant solutions, for example Titaniumand other noble materials. A similar component 903, also preferablyinjection molded, is bonded to the top of component 902. Desiccant isintroduced through inlet 905 and spreads generally evenly through theholes 904. Heat transfer fluid is transferred through the openings 905and exists through the openings 907. Desiccant that has run to thebottom of the wavy plates is collected by taking advantage of surfacetension in the liquid into the groove 811 and runs through the drainexit 906.

FIG. 10A shows an alternative embodiment of a wavy plate construction inwhich components 1001 and 1002, which are preferably injection molded,are connected to the top of a wavy plate 1003. Spreader plates 1013cause the desiccant and heat transfer fluid to be generally evenlydistributed. In one embodiment an additional injection molded component1004 provides the collection of the heat transfer fluid inside the wavyplate 1003. A membrane or other suitable material such as a wickingmaterial 1005 is applied over the top of the assembly. An example ofsuch a membrane is hydrophobic Poly Propylene manufactured by Celgardunder the tradename EZ2090. An example of a wicking surface is ahydrophilic cardboard sheet material similar to coffee filter paper. Thecompletely mounted assembly 1007 is then connected to a final injectionmolded component 1006 in such a way that the membrane or wickingmaterial guides the desiccant into the component 1006. In the finalassembly 1008 the liquid channels for the desiccant 1009 and 1012 areshown, as are the channels for the heat transfer fluid 1010 and 1011. Ifthe material 1005 comprises a membrane, then draining the liquiddesiccant from the wavy plates can become a challenge since the top ofthe assembly can “lock” the desiccant in place (also known as vacuumlock). Holes 1014 are purposely provided to allow air to enter behindthe membrane so that the liquid desiccant can easily fill and drainbehind the membrane. These holes also keep the membrane fromaccidentally getting pressurized, which could result in damage ordeformation of the membrane. Advantageously, the holes are locatedslightly above the outlet of the desiccant as can be better seen in FIG.11A. It can also be seen in 1008 that two wavy plate assemblies havebeen joined together to form a small stack of plates. It should beobvious to those skilled in the art that the assembly of wavy plates canso be stacked as to generate any amount of air treatment as desired bysimply adding additional plates to the stack.

FIG. 10B shows a detailed cross section of two hydrophobic materialssuch as membranes 1051 with a hydrophilic wicking material 1052. Sincemicro-porous membranes or similar materials are usually made to behydrophobic, the application of a membrane can have non-uniform wettingcaused by the liquid (such as—by way of example—a salt solution orwater) to be repelled by the membrane. The repellent forces result innon-uniform flow of liquid on the back of the membrane. By using ahydrophilic material 1052, the wicking effect of the hydrophilicmaterial causes the liquid to evenly distribute behind the membraneresulting in significantly increased evaporation through the membraneand a significantly increased active area. A liquid running inside thewicking material will spread uniformly between the two membranes.

FIG. 10C shows a hydrophilic material 1052 behind a hydrophobic materialsuch as a membrane 1051, attached to a thermally conductive support wall1053 (which can be, e.g., a wavy plate). If the support wall is alsohydrophobic such as is often the case with plastics and the like, thenthe wicking material will ensure even flow distribution of the liquid.The support wall can be made to be thermally conductive which wouldallow one to adjust the temperature of the liquid inside the wickingmaterial and thereby control the evaporation of absorption through themembrane.

FIG. 10D shows a similar structure as in FIG. 10C wherein the wickingmaterial is applied on both sides of the (thermally conductive) supportwall 1053. The liquids inside the wetting materials 1052 on each side ofthe wall can now be made to be different. For example, the leftmostwicking material could be wetted with a salt solution and the rightmostwicking material could be wetted with water or some other heat transferfluid.

FIG. 10E shows a structure similar to FIG. 10D wherein the support wall1053 is now made to be hollow such that a heat transfer liquid 1054 canbe used inside the support wall. Such a structure allows heat transferfrom the heat transfer fluid 1054 through the walls into the wickingmaterials 1052 on either side of the wall 1054. It should be obvious tothose skilled in the art that other combinations of hydrophobic andhydrophilic materials can be devised.

FIG. 11A depicts additional details of the construction of such as stackof wavy plates. A stack of wavy plates 1101 can be set up to treat airmultiple times by stacking the plates vertically as well ashorizontally. Vertical stacking allows air to be treated for instance toincrease dehumidification, whereas horizontal stacking increases theoverall capacity of treated air. Detail 1102 shows a detail of thebottom of the wavy plate construction in which the membrane or wickingsurface 1005 is used to guide the desiccant into the bottom drain 1006.The lower edge 1111 of the membrane or wicking material is not fixedlyconnected so as to avoid potential pressure buildup of desiccant whichcould lead to damage of the membrane or wicking surface. Detail 1107shows the same area as detail 1102 except with the membrane 1005removed. The channels 1109 and 1110 that are created in the components1004, 1006 and 1003 allow for the membrane 1005 to be bonded, but stillallow for the desiccant to pass through the channels. Similarly detail1103 of the top of the wavy plate assembly shows how the desiccant isable to enter through supply channel 1012 and run through the channelsin components 1002 and over the surface of wavy plate component 1003. Itshould be clear from the details that the holes 1014 and the unconnectededge 1111 at the bottom advantageously serve the function to 1) inhibitvapor lock at the top of the assembly and 2) to avoid pressure damage tothe membrane or wicking surface at either the top or the bottom of theassembly. Again detail 1108 shows the same top assembly with themembrane 1005 removed. Since the surface area of the wavy plate assembly1101 is important for the overall air treatment capacity of the system,it should be easy to stack multiple wavy plates in both the horizontaland vertical direction as discussed above. Features 1104, 1105 and 1106allow for stacking of plates by aligning and locking plates together. Itshould be clear to those skilled in the art that such features can havemany shapes and sizes.

FIG. 11B shows a system setup similar to FIG. 5 wherein the wavy platesare accepting a horizontal air flow. In the figure the wavy plates formtwo stacks in such a way as to treat the air passing through twice. Byplacing the wavy plates at a small angle to the incident air, the airwill interact more readily with the liquid desiccant on the surface ofthe wavy plate. Such liquid desiccant can be located behind a membraneor in a wetting material as described before. By maintaining the wavyaspect in the vertical direction, any thermal stresses caused by thermalexpansion and contraction of the wavy plates are significantly reduced.

FIG. 11C illustrates the setup from FIG. 11B in a top-down view.

FIG. 11D shows the dual set of wavy plates from FIG. 11B implementedtwice. The first set treats air coming from outdoors and performs adouble treatment of this incoming air. The second set receives returnair from a space and also treats it twice. In such a setup the recoveryof energy (water vapor and thermal energy) can be near complete. Thissetup allows for energy recovery while still allowing thermal energy tobe added or removed and water to be added to air coming through theplate system through the desiccant, thereby enhancing the heating orcooling of the incoming air. Conventional energy recovery systemstypically do not allow for the addition or removal of thermal energy orwater.

FIG. 11E illustrates a desiccant cooling system in the prior art. Astack of plates 1134 is placed (typically about 0.25 inch apart) and iscovered by a membrane 1131 that has water 1133 flowing behind it. Theopposite site of the plate contains a second membrane 1135 behind whicha liquid desiccant is flowing. Incoming air 1136 is dehumidified becausewater vapor in the air is absorbed into the liquid desiccant through themembrane 1135. At the exit of the plates, the dehumidified air 1137 ispartially directed towards the space being cooled and a portion isdirected in the reverse direction 1138. This secondary air flow 1138 isrelatively dry and can effectively absorb water vapor from the water1132 behind the membrane 1135. The absorption of water vapor through themembrane into the air leads to a cooling effect of the diverted air.This cool air in turn cools the water 1133. The cool water thenthermally cools the plates as well as the liquid desiccant whichultimately leads to the main air stream being cooled. This approachallows evaporative cooling to occur in climates such as Miami, Fla.where humidity levels and temperatures are relatively high so thatcooling towers normally do not function as well. By first drying theincoming air and then using indirect evaporative cooling through themembrane, the system is able to use evaporation to create a coolingeffect. To inhibit the secondary air from mixing with the outdoor air,it is diverted by diverter 1139 near the end of the plate stack in adirection 1140 perpendicular to the drawing. As can be seen in thefigure, the membrane/liquid layers are mirrored—water is facing waterand desiccant needs to face desiccant for each of the plates. Thiscreates a challenge for manufacturing such a plate stack.

FIG. 11F illustrates an embodiment of the concept of FIG. 11E whereinwavy plates 1147 are used to provide and alternating structure forliquid desiccant and water. In some embodiments, the wavy plates aremade using thermally conductive plastics. The wavy plates contain ridges1146 to support the membranes 1131 and 1135. Liquid desiccant enters thewavy plate set through channel 1141 and exists through channel 1144.Water enters through channel 1142 and exits through channel 1143. Anadjustably connected air diverter 1145 takes a controllable amount ofair in directs it in the reverse direction 1138. The diverted air 1138absorbs water from behind the membrane 1135. The diverter 1139 closesthe top of the opening between the plates and directs the airflow 1140in a perpendicular direction. The bottoms and tops of the wavy plates1147 are inserted into an injection molded component 1006 similar indesign to FIG. 10A.

FIG. 11G shows a detail of FIG. 11F wherein a close-up of the wavyplates 1147 that have the membranes 1131 and 1135 mounted to the ridges1146 on the wavy plates. In order to provide liquid to opposite faces ofthe wavy plates, holes 1150 and 1151 are provided in such as way is toprovide access to alternating sides of the wavy plates 1147. The liquiddesiccant enters the drain channel 1144 through the holes 1152. As canbe seen from the figure, the wavy plates 1147 can be made to begenerally identical, except that the wavy plates are flipped upside downin an alternating fashion.

FIG. 11H shows a detail of the wavy plates 1147. The wavy plates arealternatively flipped upside down to provide opposing connections to thewater and desiccant supply lines. As can be seen in the figure, theridges 1146 provide support for the membrane and the thermallyconductive surface 1134 provides a thermally conductive path to theopposite side of the wavy plate. The holes 1153 provide a uniformdistribution of the liquids similar to the holes in component 1013 inFIG. 10A.

In various embodiments described herein, wavy plate structures are usedto expose a liquid desiccant to an air stream through a membrane whilesimultaneously exposing the liquid desiccant to a heat transfer fluid.Various alternate structures can also be used to perform thesefunctions. For example, FIGS. 11I and 11J illustrate a tubular structurefor exposing a liquid desiccant to an air stream through a membranewhile simultaneously exposing the liquid desiccant to a heat transferfluid. The structure comprises a plurality of tubes 1181 that can bemade from any suitable thermally conductive material for example from athermally doped polymer extrusion. The inner wall of the tube canfeature ridges 1184 to allow a membrane 1182 to be bonded to the top ofthe ridges in such a way that the membrane is held at a small distanceto the tube wall so that liquid desiccant can pass between the wall andthe membrane perpendicular to the plane of the figure in the so createdchannel 1183. Air can thus be passed in the center of the tubes 1186,while heat transfer liquid can pass in the generally triangular sections1185 between tubes. The heat transfer fluid is thus able to heat thedesiccant solution through the thermally conductive walls. It should beunderstood that other shapes and arrangements of tubular structures canalso be devised. FIGS. 11I and 11J also show that it would be possibleto apply some wavy shape to the tube which as in the previous embodimentfunctions to achieve better interaction between air and desiccant whileat the same time reducing stresses due to thermal expansion in thevertical direction of the structure.

FIG. 11L is a top view of an alternate hexagonal structure of thermallyconductive surfaces 1192 in accordance with one or more embodiments.FIG. 11K is a three-dimensional view of one of the hexagonal elementsforming the hexagonal structure. Each hexagonal element in the structureincludes thermally conductive surfaces 1192. Ridges 1194 allow membranes1191 to be mounted substantially parallel to the thermally conductivesurfaces. The channels between the membrane 1191 and the walls 1192 insome of the elements can be used for passage of a heat transfer liquidor alternately for passage of water to perform an evaporative coolingfunction in a similar manner to the system described in FIG. 11E. In theexample shown in FIG. 11L, the hexagonal elements with channels betweenthe membrane 1191 and the walls 1192 shaded in gray contain water, andthe channels in the other hexagonal elements contain liquid desiccant.Thus, air in channels 1195 can be exposed to the liquid desiccantthrough the membranes, while already treated air 1196 can be exposed towater through the membranes.

FIG. 12 shows how the wavy plate assemblies discussed above can beintegrated into a full solar air conditioning system. The enclosure 1201provides protection of the desiccant air components from the weather.The system includes the conditioner 501 and the regenerator 502. Pumps601 provide desiccant flow to the conditioner and regenerator. Blowers1209 move air into and out of the building. Outdoor air 503 is treatedby the wavy plates and moved into the building as treated air 504.Return air 505 from the building can absorb the heat and water vapor andis exhausted at 506. A small optional chiller 1203 provides sensiblecooling if needed. A solar inverter 1202 can invert the electricitycoming from a series of solar modules 1205. There is a significantadvantage for integrating a solar inverter to an air conditioning system(whether it is a conventional air conditioner or a desiccant airconditioner): a rooftop air conditioning unit already has a significantelectrical supply line going up to it. By integrating an inverter into areplacement air conditioning unit, the installation of PV or PVT modulesa dramatically simplified. Normally a solar inverter is locatedsomewhere inside the building and electrical lines are run from the roofto the inverter creating a significant amount of cost and labor. Bylocating a solar inverter inside an air conditioner there is no need torun any electrical cabling into the building, since the existingelectrical lines to the air conditioner can be back-fed by the inverterto supply electrical power to the building. Also in the figure is showna supplemental water heater 1204 that can be used when the PV-Thermalmodules do not provide adequate temperatures or power. In addition thesolar modules 1205 can have a water storage tank 1206 in such a way thataccess hot water can easily be stored. In this system the hot water tank1206 is functions to provide ballast to the PVT module. Normally aconcrete block or similar ballast would be provided to hold down solarmodules on a flat roof However, by using a thin flat tank like 1206, weachieve two objectives: hot water storage as well as ballast. It shouldfurther be noted that each solar module can have its own storage tank.By integrating tanks 1206 below the PVT modules 1205, all electricallines 1207 and heat transfer fluid lines 1208 can be led to thedesiccant system 1200 without the need for any lines entering thebuilding or for installing tanks or inverters anywhere in the buildingthereby significantly improving installation time for the system.

FIG. 13A illustrates how such a storage system as shown in the previousfigure can be used. At the start of the day, 1301 the PVT modules 1304start receiving solar radiation 1306. The storage tanks 1305 underneaththe PVT modules are generally filled with cold water (or some other heattransfer fluid). The PVT modules start generating hot water which isdirected to the solar air conditioning system 1200, and specifically tothe regenerator 1310. Since sensible cooling also needs to be provided,one of the cold water tanks is connected to the conditioner 1309. As theday progresses 1302, the PVT modules will generate excess hot waterwhich can be used to start filling up some of the tanks The connection1307 and 1308 are made in such a way that the correct number of tanks isconnected to the air conditioner 1200. At the end of the day 1303, mostor all of the tanks will contain hot water. This hot water can now beused to continue to run the regenerator during the evening and night byconnecting the hot tanks through lines 1316 to the regenerator as shownin FIG. 13B. Since PVT modules are also relatively efficient at sheddingheat by radiation 1314, the PVT modules can now be directly connected tothe conditioner by lines 1315. In the middle of the night 1312, theradiation from the PVT modules can be used to start making cold waterfor storage in the tanks in such a way that by the end of the night allhot water has been used and cold water has filled the tanks underneaththe modules. This allows the cycle to start over again. Effectively thisarrangement allows the day to night shifting of cold and hot watergeneration, which can eliminate the need for any sensible cooling systemsuch as the small chiller 1203 in FIG. 12.

FIG. 14A shows an embodiment of the solar PVT modules from FIG. 12 insome level of detail. The PV laminate 1401, which can either be siliconor thin film based, generates the electrical power. The storage tank1402 doubles as a hot liquid storage container as well as a ballastingsystem. FIG. 14B shows a cut-out close-up of the system. A series ofthin channels 1405 behind the laminate 1401 collect heat from thelaminate and heats the transfer fluid. The main hot water channel 1404brings water down to a thermostatic valve assembly 1403. Thethermostatic valve can direct hot water either directly to the mainmanifold 1406 or to the storage tank 1402. The thermostatic valve caneither be operated automatically or through a software control.

FIGS. 15A and 15B demonstrate another use of the storage tank underneaththe PVT module. The storage tank is this case has a removable lid 1501and a main body 1502. The side and rear supports 1504 of the PV laminate1503 are removably connected to the tank and the PV laminate. Afterremoving the lid 1501, the entire solar module and support structure canbe put inside the tank body thereby protecting the solar module duringshipment. This alternate use of the tank as a shipping container can bevery helpful when solar modules have to be setup and disassembled on aregular basis for example as may occur for remote military basis. Ineffect, the tank now serves three functions: shipping container, storagetank and ballast system.

FIG. 16A demonstrates a schematic of the setup of a solar airconditioning integrated to a desiccant system for extreme summeroperation. All of the desiccant from the conditioner 501 is sent to theregenerator 502. The advantage of the plate structures is that in effectthe plate sets 501 and 502 are three way heat exchangers between air,liquid desiccant and a heat transfer fluid. This allows for PVT modulesto be tied in at two places: directly heating the heat transfer fluid at1601, or heating the desiccant through a heat exchanger at 1602.Similarly the cold connections for sensible cooling can either be madeon the desiccant side 1604 or on the heat transfer fluid side 1603.

FIG. 16B shows a setup for summer non-extreme operation. The majordifference with the previous case is that only a portion of thedesiccant is send through the heat exchanger 513. The flows of desiccantat 1609 and 1610 can be adjusted so that only a portion of the desiccantis send to the regenerator. As in the previous case, the PVT modules canbe tied in at two places: at the desiccant side 1606 and at the heattransfer fluid side 1605. Again the cold connections can be made oneither the desiccant 1608 or the heat transfer fluid 1607. It will beclear to those skilled in the art that all the heat sources and coldsources can be supplemented by other sources tied into the same lines inparallel or in series to the PVT modules or cold sources in thedrawings.

FIG. 17A shows a liquid desiccant system set up for winter heating inextreme conditions. Since active cooling of the leaving air is notnecessary, the cold sources have been omitted from the drawings. AgainPVT modules can be tied into desiccant side 1705 or the heat transferfluid side 1706. Since the heated desiccant will also emit water vaporadditional water may have to be added at 1707 to prevent highconcentrations of desiccant and potential crystallization of thedesiccant salts. Furthermore the treated air 504 may require additionalhumidification 1703 which again can be done more efficiently bypreheating the water at 1704 with PVT modules or another heat source.

FIG. 17B shows a similar setup to FIG. 17A except for non-extreme winterconditions whereby only a portion of the desiccant is send through theheat exchanger at 1708 and 1709.

FIG. 18A shows how the PVT module array from FIG. 13A can be connectedto the liquid desiccant system. PVT modules 1804 receive heat and thehot heat transfer fluid is send to both the desiccant regenerator 502and the hot storage system 1803. The cold side can draw cold water fromthe cold storage tanks 1805. At night, FIG. 18B shows how theregenerator is now drawing from the hot storage tanks 1803 whereas theconditioner is radiating heat through the PVT modules 1804, which at thesame tank provide cool water in the cold storage tanks 1805.

The setup from FIGS. 18A and 18B works well when there is a largetemperature difference between night and day temperatures, e.g., as isthe case in desert or in the central valley in California. However inother climates the temperature may not chance as much and additionalsensible cooling can still be required. As discussed before suchsensible cooling can be provided with a small chiller or a heat pump. Itshould be clear to those skilled in the art that other means of coolingsuch as Peltier cooling or evaporative cooling could be employed. Inclimates such as Miami, Fla. evaporative cooling is not as effective inthe summer due to the already high humidity levels.

FIG. 19A shows an alternative method for cooling that uses a portion ofthe dehumidified air 504 and directs it to a third set of platestructures 1904. The diverted air flow 1903 is already treated and lowin humidity. Instead of desiccant, the third set of plate structures haswater running over its surface and behind a membrane or wicking surface,and has a heat transfer fluid internally to the plates 1907. Thediverted air is now directed between the wavy plates in effect creatingwhat is known as an evaporative chiller using the wavy plates. Water issupplied to the third set of plate structures at 1905 and un-evaporatedwater is returned to the top of the plates through line 1909. Theportion of air 1903 that is diverted can be adjusted with louvers orbaffles or some other suitable mechanism in such a way that the amountof air is variable. Varying the amount of air will regulate thetemperature achieved in the building by the entering air 504. As in FIG.18B, PVT modules 1807 can be used at night to enhance the cooling effectand cold water can be stored in tanks 1805. It would also be conceivableto locate the third set of plate structures 1904 (partially) underneaththe conditioner 501. This will increase the height of the overall stack,but negates the need to redirect the air 504 in the opposite direction.Conversely it would also be possible to divert the air 504 out of theplane of the drawing and into the third set of wavy plates in ahorizontal flow pattern. Locating the third set of wavy platesunderneath the conditioner plates 501, has as a disadvantage thatreversing the air flow for winter operation such as is shown in FIG. 20Abecomes impossible. However, drawing a portion of the air 504 outperpendicular to the plane of the drawing and sending it through thethird set of wavy plates 1904 in a horizontal fashion, still will allowthe air in the third set of plates to be used for winter heating as isshown in FIG. 20B.

In addition to the third set of plates, FIG. 19A shows anotherimprovement to the desiccant system. Desiccant storage system 1902 usesthe fact that dilute desiccant will physically separate fromconcentrated desiccant if flow rates are low and the desiccant hassufficient time to settle. In other words if left alone theconcentration in tank 1902 will tend to increase going from the top tothe bottom. One can take advantage of this effect by connecting thedesiccant lines at the appropriate heights along the sides of the tank.One can also draw the desiccant from a variable height in the tank usinga vertically adjustable drain 1908. By moving the drain 1908 up, thesystem will drawer lower concentration desiccant resulting in lessdehumidification. In effect this gives the system a control capabilityfor humidity in the building. Lowering the drain 1908 will decrease thehumidity in the building but will also result in higher costs for theregeneration. In effect this now gives the system independent controlover temperature of the air by adjusting the supplemental heating system1901 is used when the PVT modules 1804 do not generate adequate heat.

It should be understood that various features and elements (such as,e.g., the tank 1902) described in connection with particularembodiments, can also be implemented in other embodiments though notexplicitly indicated.

FIG. 19B shows the system of FIG. 19A wherein the third set of wavyplates 1904 that function to provide chilled water to the conditioner501 are now also providing chilled water 1956 to one or more ceilingpanels 1955, a so-called “chilled ceiling”. This approach allows thechilled water produced in the third set of plates to also providesensible space cooling in an integrated approach. The cooled and driedair 504 and 1952 is typically guided through a series of ducts 1953 anddelivered to the space 1954 in the building 1951. This approach allowsfor easily balancing of the buildings requirements for latent andsensible cooling by varying the number of plates in the plate sets andby adjusting the desiccant concentration which in turn affects thehumidity in the space. It should be clear to those skilled in the artthat in stead of chilled ceiling plates a series of fan coils or othersuitable liquid to air heat exchangers could be deployed.

FIG. 20A shows the system from FIG. 19A but set up for winter heating.Since oftentimes the heating capacity in the winter needs to be muchlarger than the cooling capacity in the summer, it is now possible touse the third set of wavy plates as part of the heating of the incomingair. Instead of flowing water over the surface of the third set ofplates, the system is now using the liquid desiccant to treat the air.In winter mode the supplemental heater 1901 does not need to be used andneither does heat need to applied to the heat transfer fluid in loop2001. In stead the supplemental heater 2003 can be used to heat the heattransfer fluid in the conditioner wavy plate sets 501 and 1904.Additional pre-heater coils 2006 can be used to heat the entering air503 and 1906. The desiccant 2002 that enters the regenerator 502 ispicking up heat and water vapor from the leaving air 505. As discussedfor FIG. 17A, this serves to reduce the heating requirements for theconditioner as the desiccant through piping 2004 transports this heatand water to the conditioners. Lines 2005 now connect the desiccant toalso reach the third set of wavy plates. As winter conditions oftentimesrequire humidification to occur, additional water can be added througheither the same system 1905 that is used for evaporative cooling insummer mode or by additional humidifiers 1703.

FIG. 20B shows how the air 2051 flows in substantially a verticaldirection through the third set of plates 1904 during winter heatingpushed by the fan 2053. During summer cooling the air 504 is directedout of the plane of the drawing following the arrow 2052 and directedinto a substantially horizontal flow direction by the fan 2054 which issubstantially located behind the plane of the drawing and behind thethird set of wavy plates 1904. The advantage of this approach over theapproach described in FIG. 20A is that there is no need for a reversibleair fan: instead a winter fan 2503 is used during heating season and asummer fan 2504 is used during cooling season. The fan 2505 on theconditioner is always directing air in the same vertical flow. A furtheradvantage of this approach, besides the increase in winter heatingcapacity is that the entire area of the third set of plates is activelyused in both winter and summer. The approach described in FIG. 11E hasas a disadvantage 1) that is not reversible for winter heating support,2) that the effective area, particularly for the water channels 1138 isreduced due to the manner in which air flows through the evaporativechannel 1138, and 3) that the ratio of evaporative channels 1138 overdesiccant channels 1137 is fixed, giving less flexibility to adopt thesystem to climates where maybe less evaporation is needed (sensiblecooling) and more dehumidification (latent cooling). By separating theevaporative channels into a third set of plates, the flexibility isincreased to adopt the system to various climate conditions.

FIG. 21A depicts a plate heat exchanger in accordance with one or moreembodiments. Since the desiccants used in these air conditioning systemsare typically corrosive to metals, normal heat exchanger—which istypically constructed with metal—can not easily be used unless materialshave been selected specifically for corrosive duty, which usually has anegative impact on cost. By using a flat plate construction wherein theentire units is made out of plastics, costs can typically be reduced.Desiccant enters the heat exchanger in two places, for example, hotdesiccant enters at 2101 and exits as cold desiccant at 2103, and colddesiccant enters at 2102 and leaves as hot desiccant at 2104. Thehousing 2105 contains a plate 2106 assembly that has thermallyconductive surfaces 2110. Obstructions 2109 inside the plates 2106create a long convoluted path for the desiccant. Vertical separators2107 create a long convoluted path for the fluid flowing in the oppositedirection to the fluid inside the plates. Cutouts 2108 in the verticalseparators 2107 force the opposing fluid into an up-down and left-rightdirection. It will be clear to those skilled in the art that otherconstruction approaches of thermally conductive flat plastic plates canbe used as a heat exchanger.

FIG. 21B shows an alternative arrangement of thermally conductiveplastic plates for a heat exchanger. The heat exchanger 2150 comprises astack of formed, thermally conductive plastic plates 2155 and 2157. Coldliquid enters at 2151 and is heated through the plate assembly and exitsas hot liquid at 2152. Hot liquid enters at 2153 and exits cold at 2154.Each of the plates contains a seal 2156 that is oriented in such a waythe even plates 2155 allow for flow from lower left to upper right ofthe plates 2155 and odd numbered plates 2157 have a mirror image seal2156′ that allows flow from the lower right to the upper left. Theturbulence ridges 2158 cause the liquid flow to go up and down when itmoves from the inlet to the outlet, thereby creating better heatexchange with the liquid in the next channel. The turbulence ridges canbe created by forming them into the plastic plate 2155 and 2157 such asfor example by thermoforming or casting the plastic. Alternatively,since the molding costs of forming plastics plates are substantial, itis possible to using a glue system to attached glue lines 2158 to theplates 2155 and 2157. Such glue lines can be formed by a simple XYrobotic gluing system for example using 3M Corporation's Marine 5200Polyurethane glue. The sealant lines 2156 and 2156′ can also be formedusing the same gluing system, except that the height of the sealantlines would be made about 2× the height of the turbulence lines 2155 and2157, in such as way as that when the plates are stacked the glue linessupport each other and the seal lines cover the distance between the topand bottom plates.

FIG. 21C is a cross section schematic view of the plate structure andexemplary manufacturing steps involved in using glue structures toconstruct a fluid to fluid heat exchanger as was shown in FIG. 21B. Asshown in FIG. 21C, in step A, a plate 2155 preferably made from athermally conductive, non-corrosive material is first placed in amachine that can evenly apply glue ridges 2158 in a pre-determinedpattern on one side of the plate. After the glue ridges are cured (stepB), the plate is flipped over and a second set of glue ridges 2158 isapplied to the opposite side of the plate (step C), in a similar ordifferent pattern. A number of similar plates are thus constructed inthis fashion. After the number of plates have cured (step D), a base2161 of the heat exchanger is positioned and a glue pattern 2156 meantfor sealing to the base is applied. Before curing can occur, the firstplate 2155 is placed on the seal in such a way as to adhere to theunderside of the first plate (step E). This process step is repeatedwith the other plates (step F). Finally, the top plate 2162 is placedwith a glue seal 2156′ (step G). The advantage of this constructionprocess is that it is very easy to make heat exchanger units withdifferent materials, plastics as well as metals, with virtually no setupor tooling costs. Furthermore, one can easily change the size of theheat exchanger by simply enlarging the plates and re-programming theglue machine. Traditional heat exchangers typically use formed metalplates and thus every size change can require a new die for forming themetal. These heat exchangers also often employ a cast urethane gasket,so changing sizes also will often require a new casting mold.

In certain situations it could be desirable to capture the water vaporin outdoor air and turn it into liquid water, for example, to generatedrinking water. FIG. 22 shows an arrangement whereby two sets wavyplates have been integrated into an enclosure 2201. A first wavy plateset 2202 has—as before—a hot heat transfer liquid generated by a heatsource 2211. Desiccant from a source 2203 is directed to the surface ofthe wavy plates 2201. The heat from the source 2203 causes water vaporto evolve from desiccant on the surface of the wavy plates. Air 2205that is driven between the plates by the fan 2206 absorbs the watervapor and is moved to the right side of the system. Since the completesystem is enclosed and the air is unable to escape, the relativehumidity in the enclosure 2201 will reach close to 100%. When theheated, moist air 2205 exits from the first set of wavy plates, it willbe close to saturation. When that same air reaches the second set ofwavy plates 2207, the cold water loop 2208 causes the water vapor tocondense on the surface of the wavy plates 2207 and is then collected atthe bottom of the wavy plates 2207 in the form of liquid water thatflows out of the system at 2210. The cooler air 2204 exits the bottom ofthe wavy plates 2207 and is transported back to the first set of wavyplates 2202, where it is heated again and where it absorbs water vaporfrom the desiccant, which starts the cycle over again. It is possible toadd a vacuum pump 2209 so as to operate the system of FIG. 22 at reducedpressure. This would lower the required temperature to evolve watervapor from the desiccant on the first wavy plate set 2202, but wouldmake the system more complicated, for example one would also have to adda pump mechanism to retrieve the condensed water from the system atoutlet 2210 and to prevent the backflow of the desiccant on the firstset of wavy plates 2202. An optional air to air heat exchanger 2212could be added, but that could lead to condensation in the heatexchanger, which would be more difficult to recover. It should be clearto those skilled in the art that the condensation in the wavy plates2207 could be accomplished in other was such as a set of metal platesthat are relatively cool as compared to the wavy plates 2202. Sincethere is no desiccant involved in the condensation process, any suitablematerial such as metal plates can be used for the condensing component.

FIG. 23 shows a system that uses a liquid desiccant for thedehumidification of greenhouses. Conditioners 2322 and 2323 containliquid desiccant conditioners as shown also in FIGS. 1A and 1B. Thespray heads 2314 spray desiccant into a cooling tower fill 2315, whichdehumidifies the greenhouse air 2317. Diluted desiccant 2316 rains downinto a collection bath 2318. Some of the desiccant 2324 is pumpedthrough the heat exchanger 2320 and reaches a regenerator 2301. Thedesiccant can be optionally heated by a PVT module heat source 2319before reaching the desiccant collector 2304 that is part of theregenerator. Some of the concentrated desiccant in the collector 2304 ispumped to a heat exchanger 2306 and/or through an optional PVT moduleheating system 2305 before being sprayed into a filter material 2303.The filter material 2303 is able to spread the desiccant over a largearea while letting air through. Air 2302 is pumped by the fan 2309through the filter material and picks up water vapor from the hotdesiccant. The hot moist air is then transported to the other side ofthe regenerator where cold water is sprayed into the air at 2321. Watercondenses from the air and collects into a collection bath 2310. Some ofthe water is pumped through lines 2312 to heat exchangers 2313 where thewater is cooled by the air stream coming through the conditioners 2322and 2323. Excess water is drained at 2311. The heat for the system isprovided by water heater 2308 or optionally by the PVT modules 2307. Theheat exchanger 2306 is needed because the corrosion of the desiccantdoes not allow direct heating by the water heater.

FIG. 24A shows a significantly more efficient water generation system.The wavy plate conditioner 2405 treats the entering air 2406 and absorbsmoisture as before into a desiccant running over the surface of the wavyplates. The leaving air 2407 is warmer and dryer than the entering air2406. Diluted desiccant is pumped through a heat exchanger 2404 andthrough an optional PVT module heater 2403 to the water recovery system2200 discussed above. Since the wavy plates in effect comprise a threeway heat exchanger, the system 2400 can be much simpler. Water heater2402 and optional PVT modules 2401 heat a heat transfer fluid 2409 whichruns through the wavy plates inside the water recovery system 2200without the need for a heat exchanger. Similarly, cooling liquid in 2408can run directly through the conditioner wavy plates 2405 without anadditional heat exchanger. This simpler system is also more energyefficient since the air flow in the conditioner is less obstructed andsince the heating and cooling in the wavy plates is done in-situ. As aresult a lower temperature heat source such as the PVT modules can beused. Water is recovered again at 2410.

The regeneration of dilute liquid desiccant should preferably beperformed at high efficiency as well as at low temperature. Multipleeffect regenerations are known in the art that have high efficiency, butgenerally also require high temperatures. High regeneration temperaturesmake it difficult or impossible to use “waste” energy sources or solarenergy sources. Generally speaking lower temperature waste energy ismore readily and cheaply available than high temperature waste energy.FIG. 24B shows a combination of the water recovery system from FIG. 22and the indirect cooling system of FIG. 19A. By combining the waterrecovery system 2200 into the regenerator plate set 502, theregeneration of desiccant becomes what is known as a multiple effectregenerator. The dilute desiccant 511 is first directed to the platesinside the water recovery system 2200. Inside the wavy plates hot water2409 is provided to evaporate water from the liquid desiccant. Theliquid desiccant exits at the water generator at higher concentrationand is directed to the plates at 515. Hot water vapor inside the watergenerator 2200 heats the water loop 2408 which in turn heats the wavyplates 502 of the regenerator. Concentrated desiccant 512 is thenreturned through the heat exchanger 513 to be reused in the conditioner.One advantage of this system is that it can regenerate at higherefficiencies than a single effect regenerator, while still operating atlower temperatures. Furthermore the recovered water 2410 can be directedthrough water line 2451 and optional cooler 2452 to the evaporativesection of the indirect cooling system from FIG. 19A, thereby reducingor even eliminating the need to provide a water supply source.

FIG. 25 shows the system of FIG. 24A with some additional improvements.Rather than sending all of the desiccant to the regenerator 2200, theseparator 2501 allows for the least concentrated desiccant near the topof the separator to be sent for regeneration and the most concentrateddesiccant to be used again in the conditioner. Combustion of fossilfuels generally results in carbon dioxide and water vapor beingproduced. Other combustion byproducts are contaminants such as NO_(x)and SO_(x) and other residual by products. Gas burner 2502 producesthese gasses if it is used in the space to be treated such as inside agreenhouse. Hot water coils 2503 absorb most of the heat generated bythe burner. The hot water is used in the regenerator 2200. Water vapor,CO2 and the contaminants such as NO_(x) and SO_(x) go through the hotwater coils and enter the wavy plates 2405. The CO2 is desired in thegreenhouse, but water vapor and other contaminants are not. In effectthe wavy plates function as what is known as a condensing boiler byabsorbing the water in the combustion exhaust, which releases additionalheat and makes the overall combustion process more efficient. But unlikea condensing boiler the desiccant is also able to absorb some of thecontamination in the burner effluents. The desiccant transports thesecontaminants with the water to the regenerator 2200 where supplementalfilters 2411 can be employed to filter these contaminants out of thedesiccant or out of the air stream in the regenerator. The arrangementin FIG. 25 allows for burning of fuels such as biogases that are not asclean burning as natural gas. Also shown in the figure is an additionalexternal cooling cool 2504 that can be added to aid in the condensationof the water.

FIG. 26 shows how some of the concepts discussed in the previous figurecan also be integrated into winter heating system as discussed in FIG.17. Water heater 2602 uses a gas burner 2601. The heated water 2604 canalso be heated by the PVT modules 1706 to heat the conditioner 501.Desiccant on the surface of the regenerator 501 absorbs water vapor andother contaminants such as NO_(x) and SO_(x) and other residual byproducts. The desiccant is transported to the water recovery system 2200through optional filters 2603 that can capture some of the contaminantsin the desiccant. Recovered water at 2608 can be drained off or can bediverted to a humidifier 1703 through lines 2609, which can optionallybe preheated by PVT modules 1704 or some other heat source. The coldloop for the condensation of water in the regenerator 2200 can be cooledby an external cooling coil 2607, but can also be cooled by runningwater to the wavy plates 502 by the lines 2606.

FIGS. 27A and 27B show three dimensional views of the desiccant systemfrom FIG. 24A set up for greenhouse heating. FIG. 27A shows theenclosure 2701 containing the desiccant conditioner wavy plates 2405.Fans 2701 can move the air through the desiccant conditioner. FIG. 27Bshows a rear view of the same system with some openings provided toillustrate the internal components. The regenerator plates 2202 receivehot water from the water heater 2402. Heat exchanger 2404 separates thehot and cold desiccants. Condenser plates 2207 collect the water fromthe system.

FIG. 28 shows how the water generator 2200 can be used in a desalinationsystem. Seawater 2803 is guided between a set of membranes 2801 thathave concentrated desiccant 2804 on the opposite side. The desiccantfunctions as a draw fluid attracting water 2802 through the membraneinto the desiccant, thereby diluting the desiccant. An optional set ofPVT modules 2806 can preheat some of the desiccant. The diluteddesiccant is now guided through the heat exchanger 2811 to theregenerator 2200. A heating system 2807 heats a heat transfer fluid thatis used in the regenerator wavy plates 2813. The heat transfer fluid canalso be heated by the PVT modules 2812. The desiccant can also be heatedby the PVT modules 2810. An external cooling loop 2808 can be employedto cool the condenser plates 2814. Pure water is recovered at point2809. The advantage if the described system is that it can operate atsignificantly lower power levels than desalination systems that useosmosis, since solution pump power can be kept very low.

Having thus described several illustrative embodiments, it is to beappreciated that various alterations, modifications, and improvementswill readily occur to those skilled in the art. Such alterations,modifications, and improvements are intended to form a part of thisdisclosure, and are intended to be within the spirit and scope of thisdisclosure. While some examples presented herein involve specificcombinations of functions or structural elements, it should beunderstood that those functions and elements may be combined in otherways to accomplish the same or different objectives. In particular,acts, elements, and features discussed in connection with one embodimentare not intended to be excluded from similar or other roles in otherembodiments. Additionally, elements and components described herein maybe further divided into additional components or joined together to formfewer components for performing the same functions. Accordingly, theforegoing description and attached drawings are by way of example only,and are not intended to be limiting.

The invention claimed is:
 1. A desiccant air conditioning system forcooling an air stream entering a building space, comprising: aconditioner including a plurality of structures arranged in asubstantially vertical orientation, said structures being spaced apartfrom each other with an air stream gap between each pair of adjacentstructures, each structure having at least one outer surface facing anair stream gap across which a liquid desiccant can flow, wherein the airstream flows through the air stream gaps between the structures suchthat the liquid desiccant dehumidifies the air stream, each structurefurther includes a separate desiccant collector at a lower end of the atleast one outer surface for collecting liquid desiccant that has flowedacross the at least one outer surface of the structure, said desiccantcollectors being spaced apart from each other to permit airflowtherebetween; a regenerator connected to the conditioner for receivingliquid desiccant from the desiccant collectors in the conditioner, theregenerator includes a plurality of structures arranged in asubstantially vertical orientation, each structure having at least onesurface across which the liquid desiccant can flow, wherein the airstream flows between the structures causing the liquid desiccant todesorb water, each structure further includes a separate desiccantcollector at a lower end of the structure for collecting liquiddesiccant that has flowed across the at least one surface of thestructure, said desiccant collectors being spaced apart from each otherto permit airflow therebetween, said regenerator further comprising aheat source for heating a heat transfer fluid used to heat the liquiddesiccant in the regenerator; a heat exchanger connected between theconditioner and the regenerator for transferring heat from the liquiddesiccant flowing from the regenerator to the conditioner to the liquiddesiccant flowing from the conditioner to the regenerator; and anapparatus for circulating the liquid desiccant between the conditionerand regenerator.
 2. The desiccant air conditioning system of claim 1,further comprising a cold source for cooling the liquid desiccant to beused in the conditioner.
 3. The desiccant air conditioning system ofclaim 1, wherein each of the plurality of structures in the regeneratorand conditioner includes a passage through which heat transfer fluid canflow, and wherein the conditioner further comprises a cold source forcooling the heat transfer fluid in the conditioner.
 4. The desiccant airconditioning system of claim 3, wherein the liquid desiccant and theheat transfer fluid flow in generally opposite directions in theconditioner and the regenerator.
 5. The desiccant air conditioningsystem of claim 1, further comprising a photovoltaic-thermal (PVT)module for further heating the liquid desiccant flowing from theconditioner to the regenerator.
 6. The desiccant air conditioning systemof claim 1, further comprising a cold source for further cooling theliquid desiccant flowing from the regenerator to the conditioner.
 7. Thedesiccant air conditioning system of claim 1, further comprising a heatpump for further heating the liquid desiccant flowing from theconditioner to the regenerator and for further cooling the liquiddesiccant flowing from the regenerator to the conditioner.
 8. Thedesiccant air conditioning system of claim 1, wherein substantially allof the liquid desiccant used in the conditioner is transferred to theregenerator through the heat exchanger.
 9. The desiccant airconditioning system of claim 1, wherein a portion of the liquiddesiccant used in the conditioner is transferred to the regeneratorthrough the heat exchanger, and wherein the remainder of the liquiddesiccant is cooled by the cold source and returned to the conditioner.10. The desiccant air conditioning system of claim 1, wherein theplurality of structures are secured within the conditioner andregenerator in a way that permits the structures to expand or contractin a direction that is generally parallel to the thermal gradient toalleviate thermal-induced stress on the structures.
 11. The desiccantair conditioning system of claim 1, further comprising a sheet ofmaterial positioned proximate to the outer surface of each structure inthe conditioner and the regenerator between the liquid desiccant and theair stream, said sheet of material guiding the liquid desiccant into thedesiccant collector for the structure and permitting transfer of watervapor between the liquid desiccant and the air stream.
 12. The desiccantair conditioning system of claim 11, wherein the surface tension of theliquid desiccant and properties of the sheet of material facilitatetransfer of the liquid desiccant to the desiccant collector.
 13. Thedesiccant air conditioning system of claim 11, wherein in eachstructure, a lower edge of the sheet of material is not fixedlyconnected to a lower portion of the structure to reduce pressure buildupof liquid desiccant.
 14. The desiccant air conditioning system of claim11, wherein the sheet of material comprises a membrane or a hydrophilicmaterial.
 15. The desiccant air conditioning system of claim 11, whereinthe sheet of material comprises a hydrophobic micro-porous membrane. 16.The desiccant air conditioning system of claim 11, wherein the sheet ofmaterial comprises a layer of hydrophobic material and a layer ofhydrophilic material between the hydrophobic material and the at leastone outer surface of the structure.
 17. The desiccant air conditioningsystem of claim 11, wherein each structure includes two opposite outersurfaces across which the liquid desiccant can flow, and wherein a sheetof material covers the liquid desiccant on each opposite outer surface,each sheet of material comprising an outer layer of a hydrophobicmaterial and an inner layer of hydrophilic material, said inner layerfacing one of the outer surfaces of the structure.
 18. The desiccant airconditioning system of claim 17, wherein each structure includes aninternal passage through which a heat transfer fluid can flow fortransfer of heat between the heat transfer fluid and the liquiddesiccant or the air stream.
 19. The desiccant air conditioning systemof claim 11, further comprising one or more vent holes in the sheet ofmaterial of each structure to enable liquid desiccant to freely flowbetween the sheet of material and the structure and inhibit vacuum lock.20. The desiccant air conditioning system of claim 1, wherein saidplurality of structures comprises a plurality of plate assembliesarranged in a substantially vertical orientation and spaced apart topermit flow of the air stream between adjacent plate assemblies.
 21. Thedesiccant air conditioning system of claim 20, wherein each plateassembly includes a convoluted plate.
 22. The desiccant air conditioningsystem of claim 1, wherein the plurality of structures comprises aplurality of tubular members arranged in a substantially verticalorientation, at least some of which include an annular passage throughwhich the liquid desiccant can flow and a central passage surrounded bythe annular passage through which the air stream can flow.
 23. Thedesiccant air conditioning system of claim 1, further comprising anapparatus for causing turbulence in the air stream entering thestructures.
 24. The desiccant air conditioning system of claim 1,wherein the air stream entering the building space flows in a generallyhorizontal direction through the conditioner and a return air streamfrom the building space or outdoor air flows in a generally horizontaldirection through the regenerator.
 25. The desiccant air conditioningsystem of claim 1, wherein the air stream entering the building spaceflows in a generally vertical direction through the conditioner and areturn air stream from the building space or outdoor air flows in agenerally vertical direction through the regenerator.
 26. The desiccantair conditioning system of claim 1, wherein each structure comprises athermally conductive plastic material.
 27. The desiccant airconditioning system of claim 1, wherein the regenerator and theconditioner are physically separated to form a split air conditioningsystem.
 28. The desiccant air conditioning system of claim 1, furthercomprising a tank connected to the conditioner for storing the liquiddesiccant used in the conditioner, wherein the liquid desiccant variesin concentration along the height of the tank, and further comprising amechanism for drawing liquid desiccant from the tank at differentselected heights of the tank in order to obtain liquid desiccant havinga given concentration.
 29. The desiccant air conditioning system ofclaim 1, wherein the heat source for heating the heat transfer fluidcomprises a photovoltaic-thermal (PVT) module.